Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA 5095, Australia.
Environ Sci Technol. 2011 Jul 15;45(14):6145-52. doi: 10.1021/es200653k. Epub 2011 Jun 28.
Lead (Pb) bioaccessibility was assessed using 2 in vitro methods in 12 Pb-contaminated soils and compared to relative Pb bioavailability using an in vivo mouse model. In vitro Pb bioaccessibility, determined using the intestinal phase of the Solubility Bioaccessibility Research Consortium (SBRC) assay, strongly correlated with in vivo relative Pb bioavailability (R(2) = 0.88) following adjustment of Pb dissolution in the intestinal phase with the solubility of Pb acetate at pH 6.5 (i.e., relative Pb bioaccessibility). A strong correlation (R(2) = 0.78) was also observed for the relative bioaccessibility leaching procedure (RBALP), although the method overpredicted in vivo relative Pb bioavailability for soils where values were <40%. Statistical analysis of fit results from X-ray absorption near-edge structure (XANES) data for selected soils (n = 3) showed that Pb was strongly associated with Fe oxyhydroxide minerals or the soil organic fraction prior to in vitro analysis. XANES analysis of Pb speciation during the in vitro procedure demonstrated that Pb associated with Fe minerals and the organic fraction was predominantly solubilized in the gastric phase. However, during the intestinal phase of the in vitro procedure, Pb was strongly associated with formation of ferrihydrite which precipitated due to the pH (6.5) of the SBRC intestinal phase. Soils where Fe dissolution was limited had markedly higher concentrations of Pb in solution and hence exhibited greater relative bioavailability in the mouse model. This data suggests that coexistence of Fe in the intestinal phase plays an important role in reducing Pb bioaccessibility and relative bioavailability.
采用 2 种体外方法评估了 12 种 Pb 污染土壤中的 Pb 生物可给性，并与体内小鼠模型评估的相对 Pb 生物可利用性进行了比较。采用溶解性生物可给性研究联合会（SBRC）测定法的肠道阶段测定的体外 Pb 生物可给性，经调整肠道阶段 Pb 溶解度与 pH 值为 6.5 时的 Pb 醋酸盐的溶解度（即相对 Pb 生物可给性）后，与体内相对 Pb 生物可利用性（R²=0.88）强烈相关。尽管该方法对于相对生物可浸出程序（RBALP）预测体内相对 Pb 生物可利用性值<40%的土壤时会出现过高值，但也观察到了强烈的相关性（R²=0.78）。对选定土壤（n=3）的 X 射线吸收近边结构（XANES）数据拟合结果进行统计分析表明，在进行体外分析之前，Pb 强烈与 Fe 氢氧化物矿物或土壤有机部分相关。在体外过程中对 Pb 形态进行 XANES 分析表明，与 Fe 矿物和有机部分相关的 Pb 在胃阶段主要被溶解。然而，在体外过程的肠道阶段，Pb 与形成的水铁矿强烈相关，由于 SBRC 肠道阶段的 pH 值（6.5），水铁矿沉淀。因此，Fe 溶解受限制的土壤中，溶液中的 Pb 浓度明显更高，因此在小鼠模型中表现出更高的相对生物可利用性。该数据表明，在肠道阶段共存的 Fe 在降低 Pb 生物可给性和相对生物可利用性方面起着重要作用。
